In recent times, with the increasing development of information communication technologies, a variety of multimedia services, and a variety of high-quality services have been developed and introduced to the market, so that demands of wireless communication services are rapidly increasing throughout the world. In order to actively cope with the increasing demands, capacity of a communication system must be increased. A variety of methods for increasing communication capacity under wireless communication have been considered, for example, a method for searching for a new available frequency band in all frequency bands, and a method for increasing efficiency of limited resources.
As representative examples of the latter method indicating the method for increasing the efficiency of limited resources, a transceiver includes a plurality of antennas to guarantee an additional space utilizing resources so that a diversity gain is acquired, or MIMO communication technologies for increasing transmission capacity by transmitting data via individual antennas in parallel have been developed by many companies or developers. Particularly, a Multiple-Input Multiple-Output (MIMO) system based on an Orthogonal Frequency Division Multiplexing (OFDM) from among the MIMO communication technologies will be called a MIMO-OFDM system.
The MIMO-OFDM system requires a variety of technologies for increasing a Tx reliability of data, for example, a Space-Time Code (STC) or Cyclic Delay Diversity (CDD) scheme to increase a spatial diversity gain, and a BeamForming (BF) or Precoding scheme to increase a Signal-to-Noise Ratio (SNR). In this case, the STC or CDD scheme has been used to increase a Tx reliability of an open-loop system which is incapable of using feedback information at a transmission end, and the BF or Precoding scheme has been used to maximize the SNR using corresponding feedback information of a closed-loop system which is capable of using feedback information at a transmission end.
The MIMO-OFDM system may spatially have one or more codewords according to a spatial multiplexing rate. If a specific structure spatially has a single codeword, this structure is called a single codeword (SCW) structure. If a specific structure spatially has a plurality of codewords, this structure is called a multiple codeword (MCW) structure.
According to the MIMO-OFDM system which uses the multiple codeword (MCW), the transmission end performs the coding or encoding process for individual streams independent of each other. The transmission end has a multiple-coder of a mapping-block for each stream. The MIMO scheme is applied to a multiple stream (i.e., multi-stream) generated by the multiple-coder, such that the resultant multi-scream is transmitted to a destination. According to the MIMO scheme used by the transmission end, the reception end detects the spatial-multiplexed reception (Rx) signal using an appropriate receiver, and receives the resultant signal.
In this case, according to the transmission scheme of the MIMO-OFDM system which uses the conventional multiple codeword (MCW), the transmission end includes an independent encoding block for each stream, such that a spatial diversity gain is reduced when each stream is detected and decoded by the reception end. Also, the number of multiple codewords (MCWs) must be equal to or less than a spatial multiplexing rate (Rank: R), such that unexpected limitations occur when the Rx scheme is used.